Where are you located?
I have a K301 from a Cub 125 that my son rebuilt and painted for a 4H project under the supervision of a small engine repair man. It's just sitting gathering dust - occassionally I'll pull the spark pug and pour a little 5W20 in the spark plug hole to keep it from freezing up.
As far as I know it will interchange with any narrow frame cub engine except the Original. Shipping would be a bear but if you are cloise to NE Kansas we might be able to make something work.